<template>
  <!-- 如果没有数据，这一块div就不展示 -->
  <div class="todo-footer" v-show="total">
    <label>
      <input type="checkbox" v-model="isAll"/>
    </label>
    <span>
			<span>已完成{{checkedTotal}}</span> / 全部{{total}}
		</span>
    <button class="btn btn-danger" @click="delectCheckedTodos">清除已完成任务</button>
  </div>
</template>

<script>
export default {
  name: 'MyFooter',
  props: ['checkAllTodos', 'delectCheckedTodos', 'todos'],
  computed: {
    // 总数
    total() {
      return this.todos.length;
    },
    // 选中的个数
    checkedTotal() {
      return this.todos.reduce((pre, todo) => pre + (todo.done ? 1 : 0), 0);
    },
    isAll: {
      get() {
        // 当勾选中的个数和总数相等且总数大于零时才checked
        return this.checkedTotal === this.total && this.total > 0;
      },
      set(value) {
        this.checkAllTodos(value);
      }
    }
  }
}
</script>


<style scoped>
/*footer*/
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>
